Britney Spears‘s ex-husbandKevin Federlineis requesting more child support for their two sons.

“We think the reasonable needs for the children while they would be in Kevin’s custody is probably three times what he’s currently receiving,” Federline’s attorney — celebrity divorce lawyer Mark Vincent Kaplan — tells PEOPLE of how much more child support he estimates Spears should pay his client.

A rep for Spears did not immediately respond to PEOPLE’s request for comment, though a source close to the singertellsEntertainment Tonight, “Kevin wants a raise in money and he can’t account for where the $20,000 is going.”

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Kevin Federline, Britney Spears

Federline filed an Income and Expense Declaration request to review Spears’s financial documents to ascertain her net earnings and how they would inform her child support payments to him; a hearing is expected in August.

“We had attempted to see if we could negotiate a voluntary increase in child support over the last several months, and we were not successful,” Kaplan says. “We’re still hoping to resolve this without judicial intervention, but that’s something that is going to be a decision they will make.”

Because Federline is the lower income earning parent, Kaplan says he is entitled to more child support.

“The standard of living of the children while the low-income parent … doesn’t have to be identical, but it’s structured in a way that the child support orders enable the children to enjoy the benefit of the standard of living both parents can provide while they’re with both parents,” Kaplan tells PEOPLE.

“Otherwise, you have a situation where when I go with Mom, I get to pick out what pony I wanna ride that day; when I go with Dad, my high point is mowing the lawn with him,” Kaplan adds.

Kevin Mazur/Getty; Splash News

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Britney Spears; Kevin Federline

Federline also touches on the disparities in lifestyles the two offered Sean and Jayden, citing Spears’s “13,264 square foot Neoclassical Italianite [sic] villa on 21 acres of land in a gated community” complete with an elevator, a library, a wine cellar and a pool house among other amenities.

RELATED VIDEO: Proud Papa Kevin Federline Takes His Three Daughters to a Dance – and They Look So Grown Up

In February,The Blast reportedKaplan alerted Spears and her legal team that he would like to re-negotiate the amount the singer pays him in child support each month.

Britney Spears/Instagram

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Spears with her sons Jayden and Sean

Then in March, The Blast reported that after Federline asked for double the $20,000 he collects monthly from Spears, the pop star’s fatheroffered to set a budgetfor Federline rather than discuss increasing child support.

Regarding the disagreement, Kaplan told The Blast in a statement: “Unfortunately, the proposal that came back amounted to no modification of support, but it indicated to me that Mr. Spears has to recognize that he is the conservator for Britney and not for Kevin.”

Spears and Federlinedivorcedin 2007 after nearly three years of marriage. In 2013 Federline married Victoria Prince, with whom he’swelcomed two daughters, Jordan Kaye, 6, and Peyton Marie, 3½. The former rapper and dancer is also dad to daughter Kori Madison, 15, and son Kaleb Michael, 13, with ex-fiancée Shar Jackson.

The“Slumber Party”singer, who isdatingtrainer and model Sam Asghari, is gearing up to take her wildly successful Las Vegas showPiece of Meon tour this summer. But in recent years the pop star has focused on motherhood over music, documenting her adventures in parenting — fromtropical vacationsto practical jokes — on Instagram.

“My kids come first in my life, bottom line,” Spears told PEOPLE exclusively in a 2015 cover story. In the same story, her mom told PEOPLE: “I am so proud of my daughter and all her accomplishments, but I am especially proud of the mom she is and the woman she has become.”

source: people.com